Field
Pyrolized organic layers and conductive prepregs made therewith are provided.
Brief Description of Related Technology
Epoxy resins with various hardeners have been used extensively in the aerospace industry, both as adhesives and as matrix resins for use in prepreg assembly with a variety of substrates.
Blends of epoxy resins with other resins are known. See e.g. U.S. Pat. No. 4,607,091 (Schreiber), U.S. Pat. No. 5,021,484 (Schreiber), U.S. Pat. No. 5,200,452 (Schreiber), and U.S. Pat. No. 5,445,911 (Schreiber). These blends appear to be potentially useful in the electronics industry as the epoxy resins can reduce the melt viscosity of oxazines allowing for the use of higher filler loading while maintaining a processable viscosity. However, epoxy resins oftentimes undesirably increase the temperature at which oxazines polymerize.
Ternary blends of epoxy resins are also known. See U.S. Pat. No. 6,207,786 (Ishida), and S. Rimdusit and H. Ishida, “Development of new class of electronic packaging materials based on ternary system of benzoxazine, epoxy, and phenolic resin,” Polymer, 41, 7941-49 (2000).
U.S. Pat. No. 8,178,606 is directed to and claims a composite structure comprising a conductive surfacing film formed on a prepreg layup, where the surfacing film comprises silver flakes distributed substantially uniformly throughout the film in a substantially interconnected, lamellar configuration. The surfacing film of the '606 patent is formed from a curable thermosetting composition, which is defined to have at least one multifunctional epoxy resin; at least one curing agent selected from aromatic primary amines, bisureas, boron trifluoride complexes, and dicyandiamide; at least one toughening agent having a functional group selected from epoxy groups, carboxylic acid groups, amino groups and hydroxyl groups capable of reacting with other components of the composition; non-conductive fillers; silver flakes in an amount greater than about 35 wt. %, based on the total weight of the composition. The surfacing film has an electrical resistivity of less than 500 mΩ/sq and a film weight in the range of 0.01-0.15 psf (pounds per square foot). The prepreg layup is comprised of a plurality of prepreg layers, each of the prepreg layers being formed from a sheet of fibers impregnated with a matrix material.
U.S. Patent Application Publication No. 2004/0071990 is directed to an electrically conductive layer, comprising a continuous or discontinuous, non-conductive first phase comprising a polyimide base polymer, and a discontinuous, conductive second phase comprising 80, 85, 90, 95, 96, 97, 98, 99 or 100 weight percent carbon nanotube particles, where the weight percent of the second phase, based upon the total weight of both phases, is in a range between any two of the following percentages: 0.10, 0.20, 0.30, 0.40, 0.50, 0.75, 1.0, 2.0, 3.0, 4.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0 35.0, 40.0, 45.0, 46, 47, 48, 49, and 50%, where the layer has a thickness between two and 500 microns, and where the layer or a precursor thereto is oriented on a molecular scale in one or more directions to provide a surface electrical resistivity between, and including, any two of the following 50, 75, 100, 250, 500, 750, 1×101, 1×102, 1×103, 1×104, 1×105, 1×106, 1×107, 1×108, 1×109, 1×1010, 1×1011, 1×1012, 1×1013, 1×1014, and 1×1015 ohms per square.
U.S. Patent Application Publication No. 2006/0052509 is directed to a carbon nanotube composition that contains a conducting polymer (a), a solvent (b) and carbon nanotubes (c).
International Patent Publication No. 2004/001107 is directed to a method of forming carbon nanotube-filled composites using miniemulsion polymerization. The carbon nanotubes are preferably single-walled carbon nanotubes. The carbon nanotubes are highly dispersed within and associated with the polymer comprising the composite.
European Patent Publication No. EP 1 600 469 is directed to a carbon fiber composite material including a thermoplastic resin; carbon nanofibers dispersed in the thermoplastic resin; and dispersing particles which promote dispersion of the carbon nanofibers in the thermoplastic resin.
International Patent Publication No. 2006/008518 is directed to a protective device for a glazed structure, in particular an aircraft windscreen, comprises at least one removable sacrificial sheet of transparent composite. The composite comprises a transparent polymeric film having on one side an electrically conductive layer formed from a dispersion of electrically conductive particles and which is coated with a transparent hard coat, with the other side having adhesive layer thereon. Sheets of the composite may be arranged in a stack so that each sheet adheres to the adjacent underneath sheet with the uppermost sheet of each stack being removable as the sheet becomes damaged and/or dirty.
International Patent Publication No. 2008/048705 is directed to surface films, paints, or primers can be used in preparing aircraft structural composites that may be exposed to lightning strikes. The surface film can include a thermoset resin or polymer, e.g., an epoxy resin and/or a thermoplastic polymer, which can be cured, bonded, or painted on the composite structure. Low-density electrically conductive materials are disclosed, such as carbon nanofiber, copper powder, metal coated microspheres, metal-coated carbon nanotubes, single wall carbon nanotubes, graphite nanoplatelets and the like, that can be uniformly dispersed throughout or on the film. Low density conductive materials can include metal screens, optionally in combination with carbon nanofibers.
International Patent Publication No. 2011/075344 is directed to metal- or metal alloy-coated sheet materials including, but not limited to, fabrics and veils which have a metal content of between one (1) and fifty (50) grams per square meter (“gsm”). The metal-coated sheet materials may be used as-is or in conjunction with prepregs, adhesives or surfacing films to provide lightning strike protection (“LSP”) and/or bulk conductivity, among other benefits, to the resultant composite article. The resultant metal-coated fabric or veil is reportedly useful as a carrier in surfacing films to impart surface conductivity; as a carrier in adhesives to form conductive adhesive-bonded joints; as an interleaf (one or more metal-coated veils) between layers of prepreg to impart surface and/or bulk conductivity as well as toughness; or to fabricate composite articles.
Notwithstanding the state of the technology, there is a need for new pyrolized organic layers that are particularly useful in making conductive prepregs, which have the capacity to generate improved conductivity without increasing the weight of the part made therefrom, and desirably decreasing the weight of the part. That need has remained unsolved, despite the state of the art, until now.